Hi.
this is a 4 X 3 matrix..
which means
a.length gives you 4 ...the no of rows..
[0][0] [0][1] [0][2] <-Now when a[i]..that is individual rows
[1][0] [1][1] [1][2] are scanned...you have columns to store
[2][0] [2][1] [2][2] values.So length is 3
[3][0] [3][1] [3][2]
Hope you got it..